JP2022541653A - Focal plane array system for FMCW LiDAR - Google Patents

Abstract

A LiDAR system (eg, a Frequency Modulated Continuous Wave (FMCW) LiDAR system) includes a Focal Plane Array (FPA). FPA systems include Coherent Pixel Array (CPA) and Diffraction Grating Stack (DGS). The CPA includes Coherent Pixels (CPs), each of which is configured to emit coherent light. The DGS includes at least one diffraction grating positioned to diffract coherent light emitted from the CPA as one or more light beams into the environment. Each of the one or more light beams is emitted at a particular angle, the particular angle being based in part on the position of the CP that produced the coherent light forming the one or more beams.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is the subject of U.S. Provisional Application No. 62/879,382 filed July 26, 2019 and July 26, 2019, the entire disclosures of which are incorporated herein by reference. 35 U.S. Provisional Application No. 62/879,383 filed on date 35 U.S.C. S. Claim priority under C§119(e).

FIELD OF THE DISCLOSURE The present disclosure relates generally to Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR), and more particularly to focal plane arrays for FMCW LiDAR systems. Regarding the system.

Conventional LiDAR systems use mechanical moving parts and bulk optical lens elements (ie, refractive lens systems) to steer the laser beam. And for many applications (eg automotive) they are too bulky, expensive and unreliable.

Lens-free Focal Plane Array (FPA) systems for LiDAR systems. The LiDAR system can be, for example, an FMCW LiDAR system. FPA systems emit one or more light beams into the environment. One or more beams are reflected and/or scattered from objects in the environment and detected by the FPA system. LiDAR systems use the detected return light to generate depth information that describes the environment. FPA systems include Coherent Pixel Array (CPA) and Diffraction Grating Stack (DGS). The CPA includes a plurality of coherent pixels (CP, Coherent Pixel). CPs can be arranged in 1D or 2D arrays. The CP emits coherent light and receives return light. A DGS includes one or more diffraction gratings arranged in series. A DGS can consist of a thin aperiodic grating that collimates the light emitted by each CP in the CPA array. The DGS directs the coherent light emitted by the CPA as one or more light beams into the environment. In some embodiments, the DGS also collimates light emitted from the CP of the CPA. The one or more light beams are each emitted at a specific output angle, the specific output angle being based in part on the position of the CP that produced the coherent light forming the one or more beams. In some embodiments, a particular output angle is unique for each CP, and the light from each CP is output by the DGS as a light beam at an angle unique to that CP.

An FPA system can scan one or more beams in 1D and/or 2D by selectively activating different CPs of the CPA. Depending on the position of the pixel within the CPA, the collimated beams exiting the DGS propagate at different output angles. Each CP thus has a unique position with respect to the DGS, and in some embodiments, the DGS is positioned from each individual CP to form a corresponding light beam that is output from the DGS at a unique angle. Positioned to diffract the emitted coherent light. This effect allows the LiDAR beam to be steered across the environment being probed. As such, the FPA system may be configured to scan one or more light beams across a portion (eg, portion) or the entire field of view of the FPA system. FPA systems can scan one or more light beams in one or two dimensions. Conversely, a light beam propagating to the DGS with a particular return angle will be focused by the DGS to one spot on the CPA. For example, the CP that emitted the beam may be the CP that receives the reflected/scattered beam.

In some embodiments, the FPA system converts off-axis light (eg, where the principal emission axis is substantially perpendicular to the CPA array) emitted from the CPs of the CPA to on-axis light (on-axis light). Axis Light), including optical elements (eg, Microprism arrays, Blazed Gratings, etc.). In this way, off-axis light emitted from the CP can be diffracted to be emitted on-axis, and on-axis light is provided to the DGS. And conversely, light reflected from the local environment can be detected from the CP after passing through the DGS and optics.

In some embodiments, the FMCW LiDAR system includes an FPA system. FPA systems include CPA and DGS. The CPA includes CPs, each CP configured to emit coherent light. The DGS includes at least one diffraction grating positioned to diffract coherent light emitted from the CPA as one or more light beams into the environment. One or more light beams are then each emitted at a particular angle, the particular angle being based in part on the position of the CP that generated the coherent light forming the one or more beams.

In some embodiments, DGS for FMCW LiDAR systems is described. The DGS includes at least one diffraction grating positioned to diffract coherent light emitted from coherent pixels (CPs) of a coherent pixel array (CPA) as one or more light beams into an environment; Each of these light beams is emitted at a specific angle, the specific angle being based in part on the individual positions of the CPs that produced the coherent light forming one or more beams.

Other advantages and features of embodiments of the present disclosure will become more clearly apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawing examples.

FIG. 4 shows a diagram of FPA system for LiDAR beam steering application based on combination of CPA with DGS according to some embodiments.

1 illustrates a LiDAR system including an FPA system according to one or more embodiments;

4 is an FPA including a DGS including a blazed grating with non-uniform grating periodicity in accordance with one or more embodiments;

4 is an FPA including a DGS including a numerically designed multi-level grating according to one or more embodiments;

4 is a diagram of a microprism array positioned on top of a CPA in accordance with one or more embodiments;

4 is a diagram of a blazed diffraction grating positioned on top of a CPA in accordance with one or more embodiments;

1 illustrates an exemplary microprism array (or equivalently, a blazed grating) arranged in two dimensions in accordance with one or more embodiments;

4 illustrates a self-contained version of an optical element according to one or more embodiments;

1 illustrates a schematic diagram of a Switchable Coherent Pixel Array FMCW LiDAR chip according to one or more embodiments; FIG.

4 illustrates four versions of coherent pixels in accordance with one or more embodiments; 4 illustrates four versions of coherent pixels in accordance with one or more embodiments; 4 illustrates four versions of coherent pixels in accordance with one or more embodiments; 4 illustrates four versions of coherent pixels in accordance with one or more embodiments;

A LiDAR system determines depth information (eg, distance, velocity, acceleration for one or more objects) about the field of view of the system. The LiDAR system may be an FMCW LiDAR system. LiDAR systems include FPA systems.

FPA systems emit one or more light beams into the environment. An FPA system may be configured to scan one or more light beams across a portion (eg, portion) or the entire field of view of the FPA system. FPA systems can scan one or more light beams in one or two dimensions. FPA systems do not use lenses to steer and/or shape one or more beams. One or more beams are reflected and/or scattered from objects in the environment and detected by the FPA system. The FPA system includes switchable CPA and DGS. The CPA includes CPs, each of which is configured to emit coherent light. A DGS includes one or more gratings arranged in series (eg, non-periodic). Additionally, in some embodiments, the DGS may also include additional diffraction gratings arranged in parallel. One or more diffraction gratings are positioned to direct (eg, through diffraction) coherent light emitted from the CPA as one or more light beams into the environment. In some embodiments, the DGS also collimates the light emitted by the CP. One or more light beams are then each emitted at a particular angle, the particular angle being based in part on the position of the CP that generated the coherent light forming the one or more beams. Each CP thus has a unique position with respect to the DGS, and in some embodiments, the DGS is positioned from each individual CP to form a corresponding light beam that is output from the DGS at a unique angle. Positioned to diffract the emitted coherent light. Thus, an FPA system can scan one or more beams in 1D and/or 2D across a field of view by selectively activating different CPs of the CPA. The return light strikes the DGS at a particular return angle, and the DGS directs the return light to a particular CP as a function of the return angle of the return light. Therefore, if the output angle of the beam composed of light from a CP matches the return angle of the return light, the DGS will direct the return light to that same CP.

In some embodiments, the FPA system also converts off-axis light emitted from the CPs of the CPA to on-axis light (e.g., the principal emission axis substantially perpendicular to the CPA array). optical elements (e.g., Microprism arrays, Blazed Gratings, etc.) to convert the light into light). In some embodiments, light propagating perpendicular to the CPA is substantially parallel to the optic axis of the CPA. In this way, off-axis light emitted from the CP can be diffracted to be emitted on-axis, and on-axis light is provided to the DGS. And conversely, light reflected from the local environment can be detected from the CP after passing through the DGS and optics. An optical element may be positioned between the CPA and the DGS, the optical element positioned to redirect off-axis light emitted by the CPA to be on-axis, and on-axis light directed to the CPA substantially parallel to the optical axis of the

The CP uses the returned light to generate one or more output signals. One or more output signals are used to determine depth information about the field of view of the LiDAR system. Depth information indicates the range to various surfaces within the field of view of the LiDAR system and may also include information describing the velocity of objects within the field of view of the LiDAR system.

It should be noted that the FPA system can steer light in at least one dimension. And, in some embodiments, the CPs are arranged in two dimensions so that the FPA system can steer the light beam in two dimensions. The ability to steer the beam without moving parts can alleviate form factor, cost, and reliability issues found in many conventional mechanically driven LiDAR systems. Furthermore, the DGS of FPA systems have a cost-effective, lightweight and compact form factor alternative to lenses in FPA-based LiDAR systems. DGS also adds an additional degree of freedom over what conventional lenses offer, potentially enabling higher performance than could otherwise be achieved.

FIG. 1 shows a diagram of an FPA system 111 according to some embodiments. FPA system 111 includes CPA 100 and DGS 110 for LiDAR. CPA 100 includes a plurality of CPs 102 . CPA 100 can be, for example, a 1D or 2D array of individual CPs. Each CP emits a beam of light perpendicular to the DGS 110, and the properties of this beam (eg, as shown by beams 103, 104) can vary depending on the position of the CP. Beams 103 , 104 propagate through DGS 110 and exit at separate angles depending on the location of the source CP within CPA 100 . For example, when CP 101 is turned on, DGS 110 transforms incident beam 103 into collimated exit beam 107 (shown in solid lines). In contrast, light from CP 102 is shown as beam 104 (shown in dashed lines) that DGS 110 outputs as collimated output beam 108 . More than one CP can be active in the array at any given time.

DGS 110 is composed of one or more aperiodic gratings 105 . Generally, DGS 110 includes multiple non-periodic gratings 105 . In some embodiments where a small number of CPs are positioned near the central axis of DGS 110, a single non-periodic grating can be used. Aperiodic gratings 105 within DGS 110 may be arranged in series and/or in parallel. For example, FIG. 1 shows multiple non-periodic gratings 105 arranged in series. In other embodiments, the DGS 110 may include multiple non-periodic gratings arranged in parallel, with at least some of the multiple non-periodic gratings also arranged in series. For example, DGS 110 may include a central region centered on the optical axis of DGS 110, surrounded by a peripheral region. In some embodiments, the central region may include a first set of one or more non-periodic gratings and the peripheral region may include other sets of non-periodic gratings arranged in series with each other. . This arrangement can allow light passing through the peripheral region to be manipulated in a different manner than light passing through the central region. For example, the central region may produce a smaller range of beam angles (eg, output beam angles) than the range of beam angles produced by the peripheral regions. In other embodiments, the number of non-periodic gratings in the central region is greater than the number of non-periodic gratings in the peripheral region. This can be useful, for example, to improve the aperture of beams emitted from CPs near the central region in a cost-effective manner.

Such gratings may have either continuously modulated phases or a set of discrete phase levels. Grating 105 can be made from a low refractive index material such as glass, or a high refractive index material such as silicon or other semiconductors. Gratings take various forms such as Surface Relief Gratings, Sinusoidal Gratings, Blazed Gratings, Step Gratings, or some combination thereof. obtain. It can be manufactured using Nano-Imprint Lithography, Deep Ultra Violet Lithography, or other manufacturing techniques available to those of ordinary skill. In embodiments where DGS 110 has multiple gratings, the gratings can be separated by medium 106 . This medium can be air or other high refractive index material such as polymer or glass, as dictated by the system parameters. One or more non-periodic gratings 105 are arranged in series with each other in the CPA 100 .

One of ordinary skill can design the diffraction grating of DGS 110 to maximize the power coupled into collimated beams from different CPs in CPA 100 . The FPA system 111 of FIG. 1 shows light emitted from the FPA system 111 into the environment, which may be reflected/scattered back into the FPA system 111 from within the environment as return light (not shown). One thing should be noted. In some embodiments, DGS 110 causes return light to be returned to the emitting CP (e.g., return light from beam 107 is detected by CP 101 and return light corresponding to beam 108 is detected by CP 102). For example, in the transmit direction, light emitted by CP passes through DGS 110 . As the beam propagates and diffracts through the stack, it is made into a collimated beam at a particular angle (eg, output beam angle). When this beam reflects from a (diffuse) surface, the light returns to the DGS at the same angle (e.g., return beam angle) as the returning light, and thus hits the DGS 110 along the return path approximately "collimated ( Collimated)” waves. In the return direction, the DGS 110 refocuses the return light onto the CP in the opposite manner. And if the reflective surface is an ideal retro-reflector, the return light will be almost perfectly refocused onto the emitting CP. Each emitting CP therefore also detects the return light it emits—this is referred to herein as the "Reciprocal System". Thus, one or more CPs emit light that DGS 110 diffracts into one or more light beams, and DGS 110 diffracts corresponding return light into one or more CPs. One of ordinary skill can design the lattice in the DGS to perform optimally for all CPs in the CPA.

FIG. 2 illustrates a LiDAR system including an FPA system according to one or more embodiments. The FPA system may be the FPA system 111 described above with reference to FIG. For example, the FPA system can be a mutual system. The FPA system includes DGS 200 , optional optics 202 and CPA 201 . DGS 200 may be substantially the same as DGS 110 and CPA 201 may be substantially the same as CPA 100. In FIG. 2, DGS 200 receives input from CPA 201, which may optionally employ optical elements 202 (eg, prisms, microprism arrays, diffraction gratings, etc.) to correct the output beam angle. It should be noted that in some cases, optical element 202 may have CPA 201 embedded therein (eg, as described below in connection with FIG. 8). DGS 200 outputs beams at various angles 207 . The CPs in CPA 201 are controlled by FPA driver 205 . One or more individual CPs within CPA 201 can be activated to emit and receive light. Light emitted by CPA 201 is produced by Q-channel laser array 204 . Q-channel laser array 204 is a laser array having Q parallel channels, where Q is an integer. Q-channel laser array 204 can be directly integrated with CPA 201 or can be a separate module packaged with CPA 201 . Q-channel laser array 204 is controlled by laser controller 206 . Laser controller 206 receives control signals from LiDAR processing engine 203 via digital-to-analog converter 208 . The process also controls FPA driver 205 to send and receive data from CPA 201 .

LiDAR processing engine 203 includes microcomputer 209 . Microcomputer 209 processes data from the FPA system and sends control signals to the FPA system via FPA driver 205 and laser controller 206 . The LiDAR processing engine 203 also includes an N-channel receiver 210 . The signal is received by N-channel receiver 210 and the signal is digitized using a set of M-channel analog-to-digital converters (ADC) 211 .

FIG. 3 is an FPA system 311 that includes a DGS 310 that includes a blazed grating with non-uniform grating periodicity in accordance with one or more embodiments. FPA system 311 is one embodiment of FPA system 111 . FPA 311 includes CPA 300 and DGS 310 . Although not shown, FPA 311 is also an optical element ( for example, prisms, prism arrays or other diffraction gratings). In some embodiments, light propagating perpendicular to the CPA is substantially parallel to the optic axis of the CPA. The optical element can also refract on-axis return light (a portion of the beam reflected from the environment) into off-axis light. As shown, CP 301 emits an expanding light beam 303 that propagates through DGS 310 . DGS 310 includes a plurality of blazed gratings 305 arranged in series. A plurality of blazed gratings 305 produce collimated light beams 306 propagating perpendicularly from DGS 310 . In this embodiment, the blazed gratings each evolve monotonically with distance from the grating center (i.e., generally increasing, but in certain parts (maintained constant and does not decrease). Conventional bulk optic lens elements have a number of drawbacks (e.g., they are relatively heavier, have a larger form factor, and are more expensive) compared to the DGS embodiments described herein. Be careful. Similarly, a second CP 302 located off-center in CPA 300 emits a light beam 304 that propagates through DGS 310 converting the light into an oblique collimated light beam 307 . Note that light from different CPs has different beam angles (eg, output beam angles) at the output of DGS 310 . Therefore, the FPA system can steer beams in all environments by selectively activating different CPs.

Note that FIG. 3 shows light emitted from the FPA system 311 into the environment, the light may be reflected/scattered back into the FPA system 311 from the environment as return light (not shown). should. In some embodiments, the stack of blazed gratings 305 is designed to be a mutual system in which return light is returned to the emitting CP (e.g., return light from beam 306 is detected by CP 301 and beam Return light corresponding to 307 is detected by CP 302).

FIG. 4 is an FPA system 411 that includes a DGS 410 that includes a numerically designed multi-level grid according to one or more embodiments. FPA system 411 is one embodiment of FPA system 111 . FPA411 includes CPA400 and DGS410. Although not shown, FPA 411 is also an optical element ( for example, prisms, prism arrays or other diffraction gratings). In some embodiments, light propagating perpendicular to the CPA is substantially parallel to the optic axis of the CPA. The optical element can also refract on-axis return light (a portion of the beam reflected from the environment) into off-axis light. As shown, CP 401 emits an expanding light beam 403 that propagates through DGS 410 . DGS 410 includes a plurality of multi-stage gratings 405 arranged in series. The multi-step grating has a non-critical thickness distribution that is designed using a method of numerical optimization. Similarly, a second pixel located off-center of CPA 402 emits light beam 404 that propagates through DGS 410 . DGS 410 converts the light into an oblique collimated light beam 407 .

Note that FIG. 4 shows light emitted from the FPA system 411 into the environment, the light may be reflected/scattered back into the FPA system 411 from the environment as return light (not shown). should. In some embodiments, DGS 410 is a reciprocal system that returns return light to the emitting CP (e.g., return light from beam 406 is detected by CP 401 and return light corresponding to beam 407 is detected by CP 402). ).

FIG. 5 is a diagram of a microprism array 502 positioned on top of CPA 100 according to one or more embodiments. Microprism array 502 is one embodiment of optical element 202 . Microprism array 502 includes an array of transparent triangular elements (at least over the band of light emitted by CPA 100) made of a material having a refractive index higher than that of the surrounding medium (eg, air). CPA 100 includes an array of individual CPs. As previously mentioned, the CPs of CPA 100 can be turned on and off one at a time and/or in groups.

Each CP includes a light emitting region that emits light according to a light emission distribution. For example, CP 101 has an emission distribution with a main emission axis 520 and off-axis boundaries 525,530. The primary emission axis 520 is the direction in which the emitting region emits the most intense light. The emission distribution can be rotationally symmetric about the primary emission axis 520 or rotationally asymmetric.

As shown, each CP emits an oblique light beam with its principal emission axis at an angle 505 . - Consequently, the light emitted by each of the CPs is off-axis light. Off-axis light is light whose principal emission axis is not parallel to an axis perpendicular to CPA 100 . In some embodiments, the axis can be the optical axis of the FPA system. In contrast, on-axis light is light whose principal emission axis is substantially parallel to the axis. As shown, the angles 505 are the same for each CP, but it should be noted that in other embodiments some or all of the angles may differ from each other. Each microprism in microprism array 502 includes one or more facets 504 . Each CP overlaps at least one facet of the microprisms. It should be noted that in some embodiments, a single microprism can overlap multiple CPs. Microprisms redirect off-axis light to on-axis light (e.g., through the material of the microprism and the shape of one or more facets 504) and similarly redirect on-axis light (i.e., return light) to off-axis light. It can be configured to be redirected (ie incident on the CP).

FIG. 6 is a diagram of a blazed diffraction grating 602 positioned on top of CPA 100 according to one or more embodiments. Blazed grating 602 is one embodiment of optical element 202 . Blazed grating 602 performs the same function as microprism array 502, except that it operates on the principle of diffraction instead of refraction.

FIG. 7 illustrates an exemplary microprism array (or equivalently, a blazed grating) arranged in two dimensions according to one or more embodiments. A microprism array may be an embodiment of optical element 202 and/or microprism array 502 . At 700, the microprism array is arranged in a 1D linear array compatible with a regular grid of identical oblique CPs. At 701, the microprism array is radially symmetric, which is compatible with the radially symmetric grid of CP. At 702, the position and orientation of the microprisms is arbitrary, which is compatible with any arrangement of CPs. For example, each microprism shown at 702 can cover one or more corresponding CPs, and in some cases each microprism at 702 covers a single corresponding CP. In all three examples, the output beam propagates at the same on-axis angle.

FIG. 8 shows a self-contained version of the optical element according to one or more embodiments. In this case, a coherent pixel array 800 (eg, one embodiment of CPA 100) includes CPs 801 embedded in a high index medium 802. FIG. The optical element is a monolithic material overmolding the coherent pixel array 800 and the surface 804 of the monolithic material is angled with respect to CP 801 such that light emitted by CP 801 is refracted to on-axis light. CP emits a light beam 803 propagating at a small angle. The beam impinges on a polished and oblique surface 504 at a small angle, causing the transmitted beam 805 to propagate perpendicularly (ie, to be substantially on-axis). In other embodiments, the angles of the surfaces may be such that the transmitted beams 8-5 are emitted at some other target angle.

FIG. 9 shows a schematic diagram of a Switchable Coherent Pixel Array (SCPA, Switchable Coherent Pixel Array) FMCW LiDAR chip 911 according to one or more embodiments. A LiDAR chip is an optical integrated circuit. A chip may include multiple basic functional sub-arrays 900 . Each sub-array 900 includes an optical input/output (I/O) port 902, an optional 1-K optical splitter 903, and one or more SCPAs 901, where K is an integer. 1-K optical splitter 903 can be passive or active. Each optical I/O is supplied by a frequency modulated light source provided by an off-chip or on-chip laser. Optical power can be distributed on-chip via an optional 1-K optical splitter to reduce the number of optical I/Os. In the illustrated embodiment, each output of 1-K optical splitter 903 is fed to a corresponding SPCA 901 . In the illustrated embodiment, each SCPA 901 includes M coherent pixels 905 and an optical switch network 904, where M is an integer. It should be noted that in some cases, one or more optical switch networks 904, optional 1-K optical splitters 903, or some combination thereof may simply be referred to as optical switches. The optical switch is configured to switchably couple the input port 902 to the optical antenna within the coherent pixel, thereby forming an optical path between the input port and the optical antenna. An optical switch may include multiple active optical splitters. In some embodiments, an optical switch optically couples the frequency modulated laser signals to each of the optical antennas one at a time during scanning of the FMCW transceiver.

An optical switch network 904 selects one or more of the M coherent pixels to transmit and receive frequency modulated light (FM Light) for ranging and detection. The coherent pixels can be physically arranged on the chip in one-dimensional arrays (eg, linear arrays) or two-dimensional arrays (eg, rectangular or regular arrays, eg, non-random arrangements such as grids). In some embodiments, selected coherent pixels transmit light into free space, receive the returned optical signal, perform coherent detection, and convert the optical signal directly to an electrical signal for digital signal processing. can. The received optical signal does not detectably re-propagate through the switch network, instead (not shown in the illustrated embodiment) the outputs are routed separately, which reduces losses. , thus improving the signal quality.

Figures 10a-10d illustrate four versions of coherent pixels according to one or more embodiments. The four versions of coherent pixels can be, for example, the embodiment of coherent pixels described above in FIG. 10a and 10b, light from an optical switch network (eg, optical switch network 904) is provided to the optical input port 1003 of the coherent pixel. A bi-directional optical 2x2 splitter 1002 splits the light into two output ports: a TX signal 1005 and a local oscillator 1006 (LO, Local Oscillator). TX signal 1005 is transmitted from the chip using optical antenna 1000 . Optical antennas emit light from an on-chip waveguide into free space, or from free space into an on-chip waveguide, such as grating couplers, edge couplers, integrated reflectors, or any spot size converter. It is a device that combines Optical antennas can typically have polarization sensitivity with much higher emission/coupling efficiencies for light with one particular polarization (eg, TE). The antenna is reciprocal, so it collects the beam reflected from the object under measurement and transmits it back to the bi-directional 2x2 splitter 1002, which passes it back between ports 1004,1006. To divide. The bi-directional optical 2x2 splitter 1002 acts as a "Pseudo Circulator" in such a monostatic configuration where the transmitter and receiver are co-located. Received signals from port 1004 and LO 1006 are combined for coherent detection by an optical mixer, which can be a balanced 2x2 optical combiner 1001 as in Figure 10a or a Hybrid Optical Hybrid 1009 as in Figure 10b. mixed. Finally, a pair of Photo-Diodes (PDs) 1007 in FIG. 10a and four PDs in FIG. 10b convert optical signals into electrical signals for beat tone detection. The version in FIG. 10a is called the Balanced Photo-Diode (BPD) version and the version in FIG. 10b is called the hybrid version. Hybrid version offers In-phase and Quadrature outputs (I/Q) that can be used to resolve velocity-range ambiguity in FMCW LiDAR systems and enable advanced DSP algorithms do. Using a bi-directional optical 2×2 splitter as a “pseudo-circulator” would replace a separate circulator for every single pixel, which is impractical for Large-Scale Arrays with hundreds of pixels. You can eliminate having. Therefore, coherent pixels can significantly reduce cost and form factor with a signal-to-noise ratio (SNR) penalty of up to 6 dB (because some of the induced optical power cannot be used for coherent detection). For example, the received optical signal can be split between port 1003 and port 1004, the latter being used for coherent detection. The coherent pixel design shown in FIGS. 10c and 10d overcomes such limitations by introducing a polarization-splitting antenna 1010 in a new structure. Light from the optical switch network is provided to the optical input port 1003 of the coherent pixel. Optical splitter 1012 splits the light into two output ports: TX signal 1015 and local oscillator 1014 (LO). A TX signal 1015 is transmitted directly from the chip using a polarization-splitting optical antenna 1010 with one polarization (eg, TM). An antenna collects the beam reflected from the object under measurement, couples the orthogonal polarization (eg, TE) into waveguide 1013, and transmits it directly to the optical mixer. In this case, the optical signal received by the antenna is not split any further by an additional splitter or "pseudo-circulator". Signals received from port 1013 and LO 1014 are mixed for coherent detection by an optical mixer, which may be a balanced 2×2 optical combiner 1001 as in FIG. 10c, or a hybrid optical element 1009 as in FIG. 10d. Finally, a pair of photodiodes (PDs) 1007 in FIG. 10c and four PDs in FIG. 10d convert optical signals into electrical signals for beat tone detection. This design implements a highly efficient integrated circulator for every single coherent pixel, enabling ultra-sensitive on-chip monostatic FMCW LiDAR. The details are further discussed in FIGS. 8-10. In some embodiments, in conjunction with FIG. 2, the coherent pixel of FIGS. 10a-10d has a separate splitter for each of the plurality of optical antennas, each splitter connecting an optical switch and a corresponding antenna. are coupled along separate optical paths between them.
Additional configuration information

The drawings and the foregoing description relate to preferred embodiments by way of illustration only. As noted above, it should be noted that alternative embodiments of the structures and methods disclosed herein are readily recognized as viable alternatives that may be employed without departing from the principles of the claims.

While the detailed description contains numerous details, these should not be construed as limiting the scope of the invention, but merely as exemplifying different examples. It should be understood that the scope of the disclosure includes other embodiments not described in detail above. Various alternatives that will be apparent to those of ordinary skill in the arrangement, operation and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims. Variations, changes and modifications of may be made. Accordingly, the scope of the invention should be determined by the appended claims and their legal equivalents.

Alternative embodiments are implemented in computer hardware, firmware, software and/or combinations thereof. Embodiments can be implemented as a computer program product substantially embodied in a machine-readable storage device for execution by a programmable processor, the method steps performing functions by operating on input data and generating output. It may be performed by a programmable processor executing an instruction language program to perform. Embodiments advantageously include at least one programmable processor coupled to receive data and instructions from, and transmit data and instructions from, a data storage system, at least one input device and at least one output device can be implemented in one or more computer programs executable on a programmable system including Each computer program can be implemented in a high-level procedural or object-oriented programming language, or assembly or machine language, as appropriate, and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, general and special purpose microprocessors. Generally, a processor receives instructions and data from read-only memory (ROM) and/or random access memory (RAM). Generally, a computer includes one or more mass storage devices for storing data files, such devices including magnetic disks, such as internal hard disks and removable disks, magneto-optical disks, and optical disks. . Storage devices suitable for substantially implementing the computer program instructions and data include, by way of example, semiconductor memory devices such as EPROM, EEPROM and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and any form of non-volatile memory including CD-ROM disks. All of the foregoing may be supplemented by or integrated with Application-Specific Integrated Circuits (ASICs) and other forms of hardware.

Claims (20)

A focal plane array system for a frequency modulated continuous wave LiDAR system, comprising:
a coherent pixel array comprising coherent pixels, each said coherent pixel being configured to emit coherent light;
a diffraction grating stack comprising at least one diffraction grating positioned to diffract coherent light emitted from said coherent pixel array as one or more light beams into an environment, each of said one or more light beams Emitted at a particular angle, said particular angle being based in part on the position of said coherent pixels that produced said coherent light forming said one or more beams. 2. The focal plane array system of claim 1, wherein said at least one diffraction grating is an aperiodic diffraction grating. 3. The at least one diffraction grating is a blazed grating, and the at least one diffraction grating has a periodicity that evolves monotonically according to the distance from the center of the at least one diffraction grating. 3. The focal plane array system of claim 2. The at least one diffraction grating is a multi-step grating, and the at least one diffraction grating has periodicity that unfolds monotonically according to the distance from the center of the at least one diffraction grating. 3. The focal plane array system of claim 2. 2. The focal plane of claim 1, wherein said at least one grating is selected from the group comprising Surface Relief Gratings, Sinusoidal Gratings, Blazed Gratings, Step Gratings. array system. The one or more beams are collimated such that each coherent pixel has a unique position with respect to the grating stack and the grating stack is output from the grating stack at a unique angle. 2. The focal plane array system of claim 1, positioned to diffract coherent light emitted from each individual coherent pixel to form a corresponding light beam. 2. The focal plane array system of claim 1, wherein the focal plane array system is configured to scan the one or more light beams over a portion of a field of view of the focal plane array system. 8. The focal plane array system of claim 7, wherein the coherent pixel array is a 2D array and the focal plane array system is configured to scan the one or more light beams in two dimensions. the one or more light beams reflect from objects in the environment to form return light;
2. The focal plane array system of claim 1, wherein said grating stack is positioned to diffract said return light into one or more coherent pixels that generated said one or more beams. the light emitted by the coherent pixels of the coherent pixel array is off-axis light;
The focal plane array system comprises an optical element positioned between the coherent pixel array and the diffraction grating stack - the optical element reverts the off-axis light emitted by the coherent pixel array to on-axis light. 2. The focal plane array system of claim 1, further comprising: positioned to direct, said on-axis light being substantially parallel to an optical axis of said coherent pixel array. A first light beam of the one or more light beams is formed from light from the coherent pixels, the first light beam is reflected from an object in the environment to form return light, and the optical beam is 3. An element receives said return light from said grating stack and redirects said received return light to off-axis off-axis return light, said off-axis return light being detected from said coherent pixels. 11. The focal plane array system of claim 10. 11. The focal plane array system of claim 10, wherein said optical element is a blazed grating and light emitted from said coherent pixels is diffracted to be on-axis. The optical element is a monolithic material overmolding the coherent pixel array, the surface of the monolithic material being angled with respect to the coherent pixels so as to refract light emitted by the coherent pixels to be on-axis. 11. The focal plane array system of claim 10. 11. The focal plane array system of claim 10, wherein said optical element is a microprism array. 11. The focal plane array system of claim 10, wherein the microprism array is an array of linear microprisms. The microprism array is an array of circular microprisms, the microprisms forming a series of rings, the coherent pixels in the coherent pixel array having a radial distribution pattern, each microprism overlaps at least one coherent pixel in the coherent pixel array. 11. The focal plane array system of claim 10, wherein each microprism in said microprism array overlaps a single coherent pixel in said coherent pixel array. the light emitted by the coherent pixel array is off-axis light;
The focal plane array system comprises an optical element positioned between the coherent pixel array and the diffraction grating stack - the optical element reverts the off-axis light emitted by the coherent pixel array to on-axis light. 2. The focal plane array system of claim 1, further comprising: positioned to direct, said on-axis light being substantially parallel to an optical axis of said coherent pixel array. The one or more light beams are formed from light from the coherent pixel array, the one or more beams reflect from objects in the environment to form return light, and the optical element is configured to diffract the light. positioned to redirect the return light received from the grating stack to off-axis off-axis return light, the off-axis return light being detected from the coherent pixels that generated the one or more beams. 19. The focal plane array system of claim 18. A grating stack for a frequency modulated continuous wave LiDAR system, comprising:
at least one diffraction grating positioned to diffract coherent light emitted from the coherent pixels of the coherent pixel array as one or more light beams into the environment--the one or more light beams each having a specific angle; wherein said particular angles are based in part on the individual positions of said CPs that produced said coherent light forming said one or more beams.

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